The erroneous notion of "once infected always infected" and thus that every person who has become infected with M tuberculosis remains so is partially comprehensible given that tuberculosis may occur years or even decades subsequent to infection with M tuberculosis. As early as 1939 Canetti summarized the then available studies that seem to demonstrate that the large majority of primary complexes become sterile after some time. While it may be submitted that tubercle have other places to hide in the host's body than at the site of primary infection, these studies provide nevertheless a strong argument for the hypothesis that most persons who become infected with M tuberculosisdo not only contain the initial infection but actually eliminate all viable bacilli entirely.
That what is measured with the tuberculin skin test is actually just an immunological response through a memory that can last for several years is evidence by the fact that BCG vaccinated persons who most likely virtually always elimated BCG from the system can be protected from BCG for at least a decade (see "Interventions" on this site) and can retain tuberculin skin test reactivity often for years following vaccination.
